1. FIELD OF THE INVENTION
This invention relates to the shell structure of a heavy-load type rod mill used for pulverizing material which subjects the rod mill to a very heavy load, and more particularly to the shell structure of a rod mill which uses a large rod.
2. DESCRIPTION OF THE RELATED ART
In crushing and pulverising material which subjects a rod mill to an extremely heavy load, such as slag produced in an ironworks, a heavy-load type rod mill is employed which uses large rods in order to treat large lumps of metals which are included in the slag. In such a case, however, since the amount of material which can be treated in one cycle is very small as compared with the size of the rod mill, the rod mill is operated under very severe conditions such as a state in which an idle crushing phenomenon occurs, namely the phenomenon of a rod directly hitting against the barrel of the rod mill, or in which ground metals disturb the normal motion of the rods.
Conventionally, since the barrel of the rod mill and trunnions are connected by a flange fitting, stress is concentrated on the flange during operation of the rod mill and, sometimes, a bolt is broken or the joint comes loose. Sometimes, stress is concentrated on the weld where the fitting flange is welded to the barrel, resulting in the generation of cracks in the weld. At other times, stress is concentrated on the position where a manhole is provided in the barrel to enable access when the liner is to be replaced, and cracking is produced in the manhole fitting position.